The Sedimentary and Geochemical Characteristics of the Upper Devonian Wutong Formation in Lower Yangtze Region
-
摘要: 总结了下扬子区晚泥盆世五通组典型的沉积构造，如风暴砾滩、冲洗交错层理、滩脊、三脊波痕、植物化石及遗迹化石埋藏相特征等。全定量分析了泥岩类的主化学组成及微量元素，其主化学组成具有高SiO2含量。高K2O/Na2O比值，低MgO, Zr, Hf组合特征显示近源沉积特征，与下伏下古生界有显著差别，B, Ga, Ba, Sr, Rb等元素反映出滨海及海陆交互的沉积环境。综合分析沉积构造、沉积地球化学及区域地质特征，认为五通组形成于弧后前陆盆地，其沉积过程是一个海侵过程，这一大地构造背景一直延续到早石炭世末。Abstract: The integration between Lower Yangtze plate and South China plate took place at the end of Silurian.The integration brought about early to meso-Devonian stratigraphic hiatus.The lower Devonian Wutong Formation forms a connecting link between the preceding and the following sedimentation which recorded the tectonic evolution in this region.Our work on the sedimentary and geochemical characteristics of the Wutong Formation may plays an important role in studying the tectonic system transformation in this region. In this paper, the typical sedimentary characteristics of Wutong Formation, such as storm gravel bank, flushing cross-stratum, beach ridge, tricrest bed ripple, plant and trace fossil taphofacies characteristics, etc., has been recorded and summarized in detail. All these sedimentary characteristics show that the Wutong Formation is a set of littoral facies sedimentary formation and this sedimentary environment is far away from that of the underbedding lower Paleozoic. The main chemical composition and trace elements of mudstone have been quantitatively analyzed.Its main chemical compositions are characterized of high SiO2 and K2O/Na2O but low MgO. The great difference in chemical composition between Wutong Formation and the underlying lower Paleozoic formations suggest the tectonic system change at the beginning of early Devonian in Lower Yangtze region, and this conclusion is consistent with the result from the sedimentary characteristics and trace elements. In trace elements, Zr, Hf compositions distribute far away from that of upper Silurian in Zr-Hf graphs and shows to be proximal environment. B, Ga, Ba, Sr, Rb etc. and their relative ratio are characterized of littoral facies and paralic sedimentation. Summing up the sedimentary and geochemical characteristics and regional geology, the authors put forwards that the Wutong Formation is a set of littoral facies sedimentary formation that occurs in back-arc foreland basin, and this tectonic background continued to the end of early Carboniferous.
-
Key words:
- Wutong Formation /
- Lower Yangtze region /
- back-arc foreland basin
-
[1] 1 安徽省地矿局区测队，安徽地质志，泥盆系和石炭系分册[M].合肥：安徽科技出版社，1989.206
2 丁道桂，李萍，吕俊祥，下扬子区晚古生代含油气盆地原型[J].石油实验地质，1987，9(3)：272～281
3 方邺森，任磊夫.沉积岩石学教程[M].北京：地质出版社，1987.337
4 科林森 J D，汤普森 D B.沉积构造(中译)[M].北京：地质出版社，1988.164
5 吕洪波.苏南五通组风暴沉积与三脊波痕[J].石油与天然气地质.1992，13(3)：284～292
6 刘英俊.元素地球化学[M]，北京：科学出版社，1984.548
7 王益友，郭文莹，张国栋.几种地化标志在金湖凹陷阜宁群沉积环境中的应用[J].同济大学报，1979，2：52～61
8 王益友，吴萍.江浙海岸带沉积物的地球化学标志[J].同济大学报，1983，4：80～87
9 吴贤涛，胡斌，王观忠.苏南皖东五通群观山组的近岸风暴沉积与潮道沉积[J]。石油实验地质，1986，8(4)：351～361
10 夏邦栋，吕洪波.一个已埋藏的造山带探讨[J].沉积学报，1990，8(2)：1～8
11 夏邦栋，吕洪波.苏浙皖地区沉积大地构造演化[J].地质学报，1988，4(3)：01～310
12 俞鸿年，卢华复.构造地质学原理[J].北京：地质出版社，1986.345
13 张国栋，朱静昌，王益友.苏皖地区晚泥盆世五通组海侵及其沉积环境讨论[J]，地质评论，1987，33(1)：69～77
14 张国栋，王益友，朱静昌等.现代滨岸风暴沉积--以舟山普陀岛骨尖岛为例[J].沉积学报，1987，l(2)：17～28
15 赵澄标.试论安徽巢县五通组沉积相[J].石油与天然气地质，1988，9：40～45
16 Weimer R J, Howard J D, Lindsay D R. Tidal Flats. In： Scholle P A, Spearing D， eds.Sandstons Depositional Environments[C]. A.A.P.G., Tulsa, Oklahoma, 1982.191～246 -
点击查看大图
计量
- 文章访问数: 689
- HTML全文浏览量: 12
- PDF下载量: 473
- 被引次数: 0
下载:
